Diagnostic Method for Proper Refrigerant Valve Operation

ABSTRACT

There is provided a refrigerant system  100  including at least one or a plurality of refrigerant flow control devices  125  for regulating operational parameters of the refrigerant system  100 , at least one sensor  135, 140  connected to the refrigerant system  100  for monitoring the operational parameters of the refrigerant system  100 , and a controller  130 . The controller  130 , which is connected to the plurality of refrigerant flow control devices  125  and to each of the at least one sensor  135, 140 , switches a refrigerant flow control device  125  of the plurality of refrigerant flow control devices  125  between a first operating state and a second operating state, separately observes a variation in an operational parameter resulting from the switching of each refrigerant flow control device  125  of the plurality of refrigerant flow control devices  125 , compares the observed variation with an expected variation due to the switching, and determines whether the refrigerant flow control device  125  is operating properly based on whether the actual variation corresponds to the expected variation. There is also provided a method for diagnostic testing of the refrigerant system  100.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to diagnostic systems and methods, and more particularly, to diagnostic systems and methods in refrigerant systems.

2. Description of the Related Art

Typically, in complex refrigerant systems, it is difficult to diagnose a malfunctioning system component. Additionally, if the problem is not identified in a timely manner, the malfunctioning or broken component can cause substantial secondary damage to other components in the system. There are numerous examples of adjustable flow control devices, e.g., valves, within a refrigerant system that can potentially malfunction, such as a compressor unloading valve and a pressure regulating valve. Vapor (or liquid) injection valve failure is a typical example as well. If the vapor injection valve failure is not detected within a reasonable period of time, i.e., hours, it can often result in compressor damage, since with the malfunctioning vapor injection valve the compressor may operate at substantially higher then designed discharge temperatures. Similarly, a malfunctioning suction modulation valve may cause abnormally low saturation suction temperatures and refrigerant flow rates resulting in potential problems concerning oil return to the compressor and proper lubrication of internal compressor components.

There is a need for a simple diagnostic/prognostic method that will allow for a timely detection of such failures, thus preventing prolonged downtime and costly repairs of the equipment.

SUMMARY OF THE INVENTION

There is provided a refrigerant system including at least one refrigerant flow control device or a plurality of refrigerant flow control devices for regulating operational parameters of the refrigerant system, at least one sensor connected to the refrigerant system for monitoring operational parameters of the refrigerant system, and a refrigerant system controller. The controller, which is connected to the refrigerant flow control devices and to each of the at least one sensor, separately and selectively switches each refrigerant flow control device between a first operating state and a second operating state, separately observes a variation in at least one operational parameter resulting from the switching of each refrigerant flow control device, and compares the observed variation with an expected variation due to the switching. The system controller determines whether the refrigerant flow control device is operating properly based on whether the actual variation corresponds to the expected variation within a predefined tolerance range.

In one embodiment, the refrigerant system has a plurality of refrigerant flow control devices. The controller is connected to the plurality of refrigerant flow control devices, and the controller switches at least one refrigerant flow control device of the plurality of refrigerant flow control devices between a first operating state and a second operating state and separately observes a variation in at least one operational parameter resulting from the switching of each refrigerant flow control device.

There is also provided a method for diagnostic testing of a refrigerant system having at least one regulating refrigerant flow control device. The method includes individually switching at least one refrigerant flow control device from a first operating state to a second operating state, in response to a diagnostic request from a controller, and separately observing a variation in at least one operational parameter of at least a portion of the refrigerant system resulting from the switching of each refrigerant flow control device. The method also includes comparing the observed variation with an expected variation due to the switching, and determining whether the refrigerant flow control device is operating properly based on whether said observed variation corresponds to expected variation within a predefined tolerance range.

In one embodiment of the method, the refrigerant system has a plurality of refrigerant flow control devices. The method is performed individually and sequentially on each of at least two selected refrigerant flow control devices of the plurality of refrigerant flow control devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary refrigerant system including a diagnostic system according to the present invention.

FIG. 2 is a graph showing changes in operational parameters in response to turning a refrigerant flow control device on or off.

FIG. 3 is a graph showing changes in pressure in response to turning a refrigerant flow control device on or off.

FIG. 4 is a graph showing changes in pressure in response to changes in the operational states of one or more refrigerant flow control devices.

DESCRIPTION OF THE INVENTION

FIG. 1 shows a refrigerant system 100 including a diagnostic system 105 according to the present invention. Refrigerant system 100 includes refrigerant lines 110 connecting system components, condenser and evaporator heat exchangers 115 cooperating with corresponding fans 150, expansion devices 120, compressor 145, economizer heat exchanger 117, and a plurality of refrigerant flow control devices 125 for regulating operational parameters of refrigerant system 100. In one embodiment, refrigerant flow control devices 125 are valves. Refrigerant system 100 may be a single-circuit system or a multi-circuit system. The schematic presented in FIG. 1 is purely exemplary; there are many possible configurations and variations of the design of refrigerant system 100 that are not shown but fall within the scope of the invention.

Diagnostic system 105 includes a controller 130, pressure sensors 135, and temperature sensors 140. Also, additional electric current sensors may be included. Sensors 135 and 140 are connected at various points to refrigerant system 100, and, for simplicity purposes, are preferably connected to lines 110. Sensors 135 and 140 assist in monitoring operational parameters, such as temperature and pressure, of refrigerant system 100 by transmitting electric signals indicative of temperature and/or pressure to controller 130.

Controller 130 is connected to refrigerant flow control devices 125 and sensors 135 and 140. Controller 130 can switch refrigerant flow control devices 125 between at least two operating states, such as “on”, i.e., a completely open position, or “off”, i.e., a completely closed position. The operating state of refrigerant flow control devices 125 may also be an intermediate position, i.e., partially open or closed, or a plurality of such intermediate positions (for example, if a refrigerant flow control device is equipped with a stepper motor). A first operating state is associated with a first position of refrigerant flow control device 125, and a second operating state is associated with a second position of refrigerant flow control devices 125.

Controller 130 receives electric signals from sensors 135 and 140, translates these signals into operational parameter information, and compares received operational parameter information with expected operational parameters. Controller 130 also separately observes a variation in at least one operational parameter in at least a portion of refrigerant system 100 resulting from switching of each refrigerant flow control device 125, compares this variation with an expected variation due to the switching, and determines whether each refrigerant flow control device 125 is operating properly based on whether the actual variation corresponds to the expected variation within a predefined tolerance range.

Controller 130 may switch refrigerant flow control devices 125 into an “on” or “off” position, or move refrigerant flow control device 125 to an intermediate position (if the refrigerant flow control device is equipped with such capability), in response to received parameter information, and may control the operation of other components of refrigerant system 100, such as compressor 145. Such actions performed by controller 130 may be required to prevent malfunctioning and permanent damage to components of refrigerant system 100. Also, controller 130 may provide information to a user, such as expected and observed parameters, and, based on this information, whether a refrigerant flow control device is in proper working order or whether there is a malfunction.

Controller 130 determines that a refrigerant flow control device 125 is operating properly if the observed variation is substantially equal to the expected variation. Likewise, controller 130 determines that refrigerant flow control device 125 is malfunctioning if the observed variation is substantially different from the expected variation. In one embodiment, a tolerance value, or minimum difference between the observed variation and the expected variation can be predetermined, so that any difference greater than the tolerance value will trigger a malfunction determination.

In another embodiment, when more than one refrigerant flow control device 125 is selected to be tested, controller 130 performs at least the switching and separately observing steps individually and sequentially on each of the at least two refrigerant flow control devices 125 to be tested. Each refrigerant flow control device 125 is individually tested/diagnosed, one at a time. During testing/diagnosis of each refrigerant flow control device 125, the operating states of other refrigerant flow control devices and other components that may have an effect on the operational parameter are unaltered. In this way, the effect on the operational parameter, if any, is known to be from the refrigerant flow control device 125 that is under test. In another embodiment, after a test of one refrigerant flow control device is completed, that refrigerant flow control device is typically returned to its normal operating state before a subsequent refrigerant flow control device is tested.

Controller 130 preferably includes a computing platform, such as a personal computer, a mainframe computer, or any other type of computing platform that may be provisioned with a memory device (not shown), a CPU or microprocessor device (not shown), and several I/O ports (not shown). Controller 130 may also include a display or other device for providing information, and a visual or audio indicator to indicate a malfunctioning component. Refrigerant system 100 may also include an interface 155 connected to controller 130 for providing information related to the observed variation and the expected variation, and for receiving input related to the expected variation and to a selection of components to be tested. The interface may also allow a user to set component parameters and to directly control components of refrigerant system 100 and/or diagnostic system 105.

There is provided a method for diagnostic testing of refrigerant system 100 having a plurality of refrigerant flow control devices 125. The method includes switching at least one refrigerant flow control device 125 from a first operating state to a second operating state, in response to a diagnostic request from controller 130. A variation in at least one operational parameter, such as temperature or pressure, of at least a portion of refrigerant system 100 is observed as a result of the switching of each refrigerant flow control device 125. The observed variation of the at least one operational parameter is compared via controller 130 with an expected variation. Based on the difference between the observed variation and the expected variation, it is determined, preferably by controller 130, whether refrigerant flow control device 125 is operating properly. In another embodiment, the method includes an initial step of observing at least one operational parameter of at least a portion of refrigerant system 100 to generate the expected variation.

Refrigerant flow control device 125 is determined to be operating properly if the observed variation is substantially equal to the expected variation. Likewise, refrigerant flow control device 125 is determined to be malfunctioning if the observed variation is substantially different from the expected variation. For example, if refrigerant flow control device 125 is broken, no change in operation occurs. If refrigerant flow control device 125 is functioning properly, then there is a step change in the corresponding operational parameter as would be expected. If there were a partial malfunction, a change or variation in the corresponding operational parameter would be observed but would be different than the expected change of this operational parameter.

For example, when pressure sensor 135, for measuring compressor suction or compressor discharge pressure, is installed on line 110 associated with suction port or discharge port of compressor 145 respectively, a change in refrigerant flow control device 125 operating state would be expected to cause a step change in pressure. If such step change is not present, refrigerant flow control device 125 malfunction is detected. A piston or plunger of refrigerant flow control device 125 can, for example, be stock or “frozen in place” due to debris present that prevents its proper movement. Likewise, a temperature step change can be detected.

A graph illustrated in FIG. 2, having a y-axis showing both a temperature value, “T_(DISCHARGE)”, a pressure value, “P_(DISCHARGE)”, and an x-axis indicating time, “t”, reveals a change in at lease one operating parameter in response to a corresponding refrigerant flow control device being moved or switched from one operating state to another. For instance, if a vapor (or liquid) injection valve is shut down, i.e., closed, the discharge temperature, shown in a solid line, should be expected to increase by a certain amount above the measurement tolerance threshold. If such a change is not observed, as shown by the dotted line in FIG. 2, the vapor (or liquid) injection valve is not operating properly and is thus not delivering enough vapor and/or liquid to cool compressor 145. Analogously, if a compressor unloading valve is closed prior to the system shutdown, a discharge pressure increase will indicate proper operation of the compressor unloading valve. The vapor injection valve and compressor unloading valve are exemplary. The graph of FIG. 2 demonstrates similar effects in other types of refrigerant flow control devices. As is shown in FIG. 2, both properly operated valves are moved to their original states at the end of the test.

Similarly, for example, partially closing a suction modulation valve should be expected to cause a suction pressure to decline. If such decline does not occur, the suction modulation valve is not functioning properly. This is shown in FIG. 3, having a y-axis representing decreasing suction pressure value, “P_(SUCTION)” corresponding to partial suction modulation valve closure, and an x-axis representing time, “t”. As shown in FIG. 3, if the suction modulation valve is at least partially closed, the suction pressure shown in a solid line is expected to decrease. The observed P_(SUCTION), shown by a dotted line, represents a malfunctioning suction modulation valve. Similarly, as shown in FIG. 3, properly operating suction modulation valve is returned to its original position after the test is complete.

Similar relationships can be established for many other refrigerant flow control devices, including but not limited to discharge valves, economizer valves, pressure regulating valves, etc. FIGS. 2 and 3 demonstrate an instance where a refrigerant flow control device is completely malfunctioning or entirely lost its control. In other instances, a refrigerant flow control device may be only partially malfunctioning, and thus a change in pressure or temperature may be observed. However, such change in temperature or pressure will not be equivalent or substantially equivalent to the expected change.

FIG. 4 demonstrates additional embodiments, and includes a y-axis representing stepwise increasing pressure value, “P”, and an x-axis representing time, “t”. One embodiment includes a refrigerant flow control device having a stepper-motor that changes position of the refrigerant flow control device in a step pattern. Proper operation of the refrigerant flow control device produces pressure values corresponding to the solid line in FIG. 4, and representing proper operation based on pre-programmed values. The dotted line shows an example of a malfunctioning refrigerant flow control device and/or stepper-motor, illustrating step values that are different than expected step values.

FIG. 4 also demonstrates an additional embodiment of the method. In previous embodiments, each refrigerant flow control device, e.g. valve, is returned to its original operating position prior to testing of a next refrigerant flow control device. In the embodiment represented in FIG. 4, each refrigerant flow control device is not returned to its original operating position, but is left in an operating position, e.g., the second operating state, at which corresponding system operational parameters were observed last. Each sequentially tested refrigerant flow control device produces another step in the at least one corresponding operational parameter, e.g., pressure value. In the present example, each valve is, for instance, closed for a test, and remains closed as subsequent valves are tested. The solid line shows proper step increases in pressure value corresponding to the shutdown of each valve. The dotted line represents at least one malfunctioning valve, as the dotted line does not correspond to the expected values as shown in the solid line. The refrigerant flow control devices, i.e., valves in one embodiment, under consideration and testing should be associated with the same at least one operational parameter.

In the instance where at least two refrigerant flow control devices 125 in refrigerant system 100 are tested, controller 130 performs the method on each designated refrigerant flow control device, one at a time, i.e., individually and sequentially, to verify the refrigerant flow control device's proper operation. During the test of each refrigerant flow control device, the operating states of all of the untested components and/or refrigerant flow control devices, particularly those that would have a potential effect on the at least one operational parameter under consideration, are unaltered so that the individual effect on the operational parameters of refrigerant system 100 by each refrigerant flow control device can be detected. For example, during a pre-shutdown diagnostic procedure, controller 130 steps through the method wherein each refrigerant flow control device under consideration is moved from an initial to a final operating state, and the change in at least one of the corresponding operational parameters is observed.

The frequency and sequence of such diagnostics for each refrigerant flow control device may be based on confidence in refrigerant flow control device reliability or criticality of its functionality for the operation of refrigerant system 100. For example, refrigerant flow control devices that have a lower reliability may be tested more frequently than more reliable refrigerant flow control devices. In one embodiment, under practical circumstances, the method can be performed once per day.

In another embodiment, in addition to the observed and expected variation values being simple differences or step values, the expected and observed variation may be a rate of change, i.e. a derivative, of the observed variation and a rate of change of the expected variation. Observing the rate of change would allow larger magnitudes of the system characteristics under observation to be registered, thus permitting detection of a malfunctioning refrigerant flow control device sooner.

The method may be performed on refrigerant system 100, or on each circuit of a multi-circuit system. The method may be performed just prior to, i.e., very shortly before system shutdown. The method may also be performed during normal operation of refrigerant system 100. In this embodiment, controller 130 issues a signal to change the position of refrigerant flow control device 125, the test of the function of refrigerant flow control device 125 is performed as described above, then refrigerant flow control device 125 is returned back to a position for normal operation of refrigerant system 100.

In another embodiment, at least one refrigerant flow control device 125 has more than two operating states, such as open, closed, and one or more various partially open states. In this embodiment, the method may be performed multiple times by switching the at least one refrigerant flow control device 125 to a plurality of operating states, and performing the steps of observing and comparing actual and expected changes in at least one corresponding operational parameter for each of the plurality of operating states.

Although this method is the most beneficial in the field, i.e., during normal use of refrigerant system 100, the method can also be successfully employed at the factory, when refrigerant system 100 is undergoing final run tests. Lastly, if performance degradation of some critical refrigerant flow control devices is monitored and recorded over a period of time, the method can form a basis for a prognostic toolbox, in which the changes in variation of at least one operational parameter corresponding to a particular refrigerant flow control device are compared overtime or with certain periodicity. Variation may be observed repeatedly over a selected period of time, and changes in the variation are observed to record and analyze degradation of at least one refrigerant flow control device. This will allow preventive maintenance of refrigerant system 100 and avoidance of undesired prolonged shutdown intervals.

One advantage of the system and method of the present invention is that it would not require any additional expenditures on any additional components, as the diagnostic-method can be accomplished simply through appropriate software changes.

It should be understood that various alternatives, combinations and modifications of the teachings described herein could be devised by those skilled in the art. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. 

1. A method for diagnostic testing of a refrigerant system 100 having at least one refrigerant flow control device 125, comprising: switching said at least one refrigerant flow control device 125 from a first operating state to a second operating state, in response to a diagnostic request from a controller 130; observing a variation in at least one operational parameter of at least a portion of said refrigerant system 100 resulting from said switching of said at least one refrigerant flow control device 125; and comparing said observed variation with an expected variation due to said switching.
 2. The method of claim 1, further comprising determining whether said refrigerant flow control device 125 is operating properly based on whether said observed variation corresponds to said expected variation within a predefined tolerance range.
 3. The method of claim 1, wherein said refrigerant flow control device 125 is a valve 125, wherein said first operating state is a first position of said valve 125, and said first operating state is selected from the group consisting of: completely open, completely closed, and partially closed, and wherein said second operating state is a second position of said valve 125, and said second operating state is selected from the group consisting of: completely open, completely closed, and partially closed.
 4. The method of claim 1, wherein said operational parameter is selected from a group consisting of temperature, pressure and electric current.
 5. The method of claim 1, wherein said system has a plurality of refrigerant flow control devices 125, and wherein said method is performed individually and sequentially on each of at least two selected refrigerant flow control devices 125 of said plurality of refrigerant flow control devices 125, and wherein during said steps of switching each said refrigerant flow control device 125 and observing said variation, an operating state of untested refrigerant flow control devices 125 of said plurality of refrigerant flow control devices 125, which have a potential effect on said operational parameter, is unaltered.
 6. The method of claim 1, wherein said refrigerant flow control device 125 is determined to be operating properly if said observed variation is substantially equal to said expected variation, and wherein said refrigerant flow control device 125 is determined to be malfunctioning if said observed variation is substantially different from said expected variation.
 7. The method of claim 1, wherein said observed variation and said expected variation is selected from the group consisting of: a change between a first parameter corresponding to said first operating state and a second parameter corresponding to said second operating state, and a rate of change in said first parameter.
 8. The method of claim 1, further comprising a step selected from the group consisting of: returning said at least one refrigerant flow control device 125 to said first operating state after observing said variation, and allowing said at least one refrigerant flow control device 125 to remain in said second operating state after observing said variation.
 9. The method of claim 1, wherein said at least one refrigerant flow control device 125 has more than two operating states, and wherein said method is performed multiple times by switching said at least one refrigerant flow control device 125 to a plurality of operating states, and performing said steps of observing and comparing for each of said plurality of operating states.
 10. The method of claim 1, wherein said variation is observed repeatedly over a selected period of time, and changes in said variation are observed to record and analyze degradation of said at least one refrigerant flow control device
 125. 11. A refrigerant system 100, comprising: at least one refrigerant flow control device 125 for regulating operational parameters of said refrigerant system 100; at least one sensor 135, 140 connected to said refrigerant system 100 for monitoring said operational parameters of said refrigerant system 100; a controller 130, connected to said at least one refrigerant flow control device 125 and to each of said at least one sensor 135, 140, that switches a refrigerant flow control device 125 between a first operating state and a second operating state, observes a variation in at least one operational parameter resulting from said switching of said at least one refrigerant flow control device 125, and compares said observed variation with an expected variation due to said switching.
 12. The system of claim 11, wherein said controller 30 determines whether said refrigerant flow control device 125 is operating properly based on whether said observed variation corresponds to said expected variation within a specified tolerance range.
 13. The system of claim 11, wherein said operational parameter is selected from a group consisting of temperature, pressure, and electric current, and wherein said sensor 135, 140 is selected from the group consisting of a pressure sensor 135, a temperature sensor 140, and an electric current sensor.
 14. The system of claim 11, wherein said refrigerant flow control device 125 is a valve 125, and wherein said first operating state is a first position of said valve 125, and said second operating state is a second position of said valve
 125. 15. The system of claim 11, further comprising an interface 155 connected to said controller for providing information related to said observed variation and said expected variation, and for receiving input related to said expected variation and from refrigerant flow control devices 125 to be tested.
 16. The system of claim 11, wherein said controller 130 determines that said refrigerant flow control device 125 is operating properly if said observed variation is substantially equal to said expected variation, and wherein said controller 130 determines that said refrigerant flow control device 125 is malfunctioning if said observed variation is substantially different from said expected variation.
 17. The system of claim 11, wherein said refrigerant system 100 has a plurality of refrigerant flow control devices 125, wherein said controller is connected to said plurality of refrigerant flow control devices 125, and wherein said controller switches at least one refrigerant flow control device 125 of said plurality of refrigerant flow control devices 125 between a first operating state and a second operating state and separately observes a variation in at least one operational parameter resulting from said switching of each said refrigerant flow control device
 125. 18. The system of claim 17, wherein said controller 130 performs at least the switching and separately observing steps individually and sequentially on each of at least two selected refrigerant flow control devices 125 of said plurality of refrigerant flow control devices 125, and wherein during said switching and observing steps, an operating state of untested refrigerant flow control devices 125 of said plurality of refrigerant flow control devices 125, which have a potential effect on said operational parameter, is unaltered.
 19. The system of claim 11, wherein said refrigerant system 100 is selected from the group consisting of a single-circuit system and a multi-circuit system.
 20. A system or method for diagnostic testing of at least one refrigerant flow control device 125 of a plurality of refrigerant flow control devices 125 of a refrigerant system 100 as herein before described with reference to any one of FIGS. 1, 2, 3 and 4 of the accompanying drawings. 